Question

Timmy is playing by a well and drops in a rock. After 6.0 seconds, the rock hits the water below. What is the velocity of the rock when it hits the water below?1) 59 m/s2) 9.8 m/s3) O m/s4) 6 m/s

Answer 1

Since the only force acting on the rock while it falls is its weight the motion of the rock is uniform accelerated motion with acceleration equal to the acceleration of gravity. This means tha the velocity when it hits the water can be obtained by the equation:

`v=v_0+gt`

In this case, since Timmy dropped the rock, the initial velocity is equal to zero. Plugging the remaining values, given in the problem, we have that:

`\begin{gathered} v=0+(-9.8)(6) \\ v=-58.8 \end{gathered}`

The minus sign indicates that the rock is falling (moving downwards). Dropping the sign and rounding our answer we conclude that the rock hit the water with a velocity of 59 m/s